Applicant claims priority from German patent application No. 101 17 597.3 filed Apr. 7, 2001.
In prior rocker switches, a spring biases the shaft toward a neutral position while allowing the shaft to turn clockwise or counterclockwise from the neutral position. The exact position of the shaft at the neutral position varies, depending upon the relative forces applied in opposite directions. It is very difficult to manufacture springs so their forces are equal, or so their forces remain equal over a long period of time. In addition to the variation of the neutral position, there is often play in the shaft, in that noticeable resistance to turning of the shaft in either direction occurs only after a slight rotation of the shaft, which is sometimes annoying. A rocker switch of simple design, which had a constant neutral position and which avoided play in the shaft, would be of value.
In accordance with one embodiment of the present invention, a rocker switch is provided, wherein the shaft that can pivot or rock clockwise and counterclockwise from a neutral position, is reliably held in a constant neutral position, without play, in a switch of simple and rugged construction. A coil spring which extends around the shaft, has front and rear opposite coil end portions with corresponding front and rear spring ends. The spring also has a spring middle that connects the front and rear coil end portions. The shaft has a pair of arms, with a first arm engaging the front spring end and a second arm positioned to engage the spring middle when the shaft turns clockwise, and to pivot away from the spring middle when the shaft turns counterclockwise. The housing has a spring center support that engages the spring middle in its neutral position and that prevents the spring middle from moving counterclockwise from the neutral position while allowing the spring middle to move clockwise from the neutral position. As a result, when the shaft turns clockwise, the front spring end and spring middle turn clockwise and the rear coil end portion is loaded. When no pivoting force is applied to the shaft, the rear coil portion holds the spring middle against the spring center. When the shaft is turned counterclockwise, only the front spring end is turned counterclockwise while the spring middle is prevented from turning, and the first coil end portion is loaded.
A ring magnet is mounted on the shaft to turn with it and operate a magnetic field sensor such as a Hall sensor. The opposite coil end portions lie beyond opposite ends of the ring magnet, and the spring middle extends across the spring magnet.
The novel features of the invention are set forth with particularity in the appended claims. The invention will be best understood from the following description when read in conjunction with the accompanying drawings.